Status epilepticus is a condition in which multiple epileptic seizures occur without complete recovery from the physiological effects of one seizure before another seizure occurs. There are as many types of SE as there are kinds of epileptic seizures. Generalized convulsive status epilepticus initially presents with repeated generalized convulsions without full recovery of consciousness between seizures. If untreated or undertreated, the convulsive activity becomes progressively subtle and is accompanied by a predictable series of progressive EEG changes. Non-convulsive SE refers to complex partial SE or absence SE, both of which exhibit an epileptic twilight state of altered contact with the environment. In simple partial SE there is no impairment of consciousness, and the behavioural changes reflect focal ictal discharges confined to one area of the cortex. There are between 65,000 and 150,000 cases of the SE in the US each year. Both acute and remote cerebral insults can cause SE, as can severe systemic disease that causes SE secondary to a toxic-metabolic encephalopathy. Mortality is high, but is largely a reflection of underlying aetiology when SE is treated appropriately and aggressively. Treatment is focused on terminating ongoing seizure activity as quickly as possible, both because the longer SE persists the more likely permanent neuronal damage will ensure and also because of strong evidence that the longer SE persists the more refractory to treatment it will be. Currently the most commonly accepted treatment protocol involves rapid initiation of therapy with intravenous lorazepam (0.1 mg/kg), followed, if necessary, by 20 mg/kg of phenytoin, followed, if necessary, by 20 mg/kg of phenobarbital. However, some neurologists still use intravenous diazepam (because of its more rapid antistatus effect) followed by phenytoin. New experimental data in the rat suggest that phenytoin followed by diazepam may be more effective, but this order of administration still has to tested in properly designed clinical trials.